The nurse receives a prescription for 0.375 mg of digoxin IV. The vial reads digoxin 0.25 mg/mL. How many milliliters will be administered?

• A. 1.0 mL
• B. 1.5 mL
• C. 2.0 mL
• D. 0.5 mL

Answer: (B)

Calculating how much to give from a labeled concentration means dividing the desired dose by the concentration to get the volume to administer. Here, you need 0.375 mg and the solution is 0.25 mg per mL. So the volume is 0.375 mg ÷ 0.25 mg/mL = 1.5 mL. Verifying: 1.5 mL × 0.25 mg/mL = 0.375 mg, which matches the order.

If you used 1.0 mL, you’d administer 0.25 mg; 2.0 mL would be 0.5 mg; 0.5 mL would be 0.125 mg. The correct amount to deliver the prescribed 0.375 mg is 1.5 mL.